The present disclosure relates to HVAC (heating ventilating air conditioning) installed duct smoke detectors and more particularly to their testing. Duct mounted smoke detectors are installed in particular locations to meet certain requirements of, for example, the Ohio Building Code, as embodied in the Ohio Mechanical Code or OMC:
1. Mounted on the return air handler ductwork for all air handlers which, individually or as part of a system, have a design capacity greater than 2000 cfm. Installed upstream of any filters, exhaust air connections, outdoor connections, or decontamination equipment and appliances. (OMC606.2.1);2. Where return air risers serve two or more stories and serve any portion of a return air system having a design capacity greater than 15,000 cfm, duct mounted smoke detectors shall be installed in each story. Duct mounted smoke detectors shall be located upstream of the connection between the return air riser and any ducts or plenums. (OMC606.2.3);3. Mounted within five foot of code required smoke dampers. (OMC607.2.1.1).
Smoke detectors are required by the National Fire Alarm Code, a published standard of the National Fire Protection Association, to be tested at time of installation and subsequently annually. The frequency of testing and the method of testing are described in Chapter 10 of the National Fire Alarm Code standard. Table 10.3.1 requires that duct detectors have a visible inspection performed semiannually, to insure that there are no changes that would affect equipment performance. Table 10.4.4 requires that a duct type smoke detector be tested or inspected to ensure that the device will sample the air stream. The test shall be made in accordance with the manufacturer's instructions.
All manufactures of duct mounted smoke detectors recommend that test smoke be generated and travel in the duct work to enter the air sampling tubes of the duct mounted smoke detector. All Ohio's certified building departments require that the duct-mounted smoke detectors be tested per the manufacturer's testing instructions. All newly constructed building's mechanical fire alarm tests, performed by the local certified building departments, require that smoke be placed in the air duct's air stream and that the test smoke set the duct mounted smoke detector into alarm.
Testing of duct-mounted smoke detectors located on the air handler supply ductwork is difficult. The diffusers and filters on the air handler stop air-born particulates; consequently large volumes of test smoke must be generated at the return air location to travel through the air handler for enough test smoke to reach the duct mounted smoke detectors on the supply ductwork. Multiple duct mounted smoke detectors on the supply side are very difficult to test because duct mounted smoke detectors located downstream of other duct mounted smoke detectors will sample the test smoke laden air and shut down the air handler and the test smoke does not reach the duct mounted smoke detector desired to be tested. Tests currently require coordinated efforts of multiple people to manually bypass previously tested detectors so that the test smoke will travel downstream to untested detectors. Because great quantities of test smoke is running through the duct work the duct mounted smoke detectors become dirty from the test smoke and need to be cleaned to stop alarming. The tests are scheduled during unoccupied building use times because the air handler systems of the building are not conditioning the air in the building properly because they are being shutdown and also because the test smoke used to test the duct mounted smoke detectors has traveled throughout the whole building.
It is to this problem that the present disclosure is addressed.